Process for isomerizing normal paraffins



Sept. 13, 1960 o. H. THOMAS ET AL 2,952,721

PROCESS FOR ISOMERIZING NORMAL PARAFFINS Filed Dec. 1, 1958 THE EFFECT OF 8091A 0N CATALYST AREA CONDITIONS: 600F, lalm.

h'CL PART/AL PRESS RD'I50 BOR/A HCL CONTACT T/ME HRS.

THE EFFECT OF BOQ/A 0N CATALYST CRUSH STRENTH CONDITIONS: 600 F aim. HCL PA RT/AL PRESSURE 400 500 HCL CONTACT TIME, HRS.

INVENTOR5 3 mpumz rfiu 1 M m T A .amorphous hydrous alumina or their mixture. alumina base can contain small amounts of. other solid .titania, zirconia, etc., or their mixtures.

catalyst, but if during use the noble metal be present in metallic form then it is preferred that it be so finely divided that it is not detectable by X-ray diffraction means, i.e. that it exists as crystals of less than 50 Angstrom units size. Of the noble metals platinum, palladium and rhodium are preferred.

p The boria component is surface dispersible on the support and seems essentially inert to hydrogen halide. It is employed in amounts suflicient to enhance the life .of the alumina support and such amounts are, therefore, preferably added in direct proportion to the area of the support. For instance, the amount of boria will usually be about 3 to 20 weight percent, and preferably about 8 to 15 weight percent, of the catalyst. These amounts are particularly efiective on alumina having surface areas of about 350 to 600 square meters per gram (BET) before .use.

long periods of time when isomerizing the C to C n-paraffins, it is necessary to provide a hydrogen halide of atomic weight between 35 and 85, e.g. HCl and HBr,

- In order for the catalyst to maintain its activity for during the processing period. The hydrogen halide is Y '5 added along with or in the n-paraifin feed in an amount of at least about 1 up to about weight percent, based on the hydrocarbon feed, preferably at least about 1% up to about 20%, and advantageously about 5 to 15 weight percent, of the hydrogen halide or of a hydrogen halogen compound or other substance which will produce the hydrogen halide under the isomerization conditions can be employed. Suitable hydrogen halide precursors of this type include the elemental halogens, chlorine and preferably about 300 to 600 p.s.i.g. The catalyst can be used as a fixed, moving'or fluidized bed or in any other convenient type of handling system. The fixed bed system seems most advantageous at this time and the space velocity will in most cases be from about 0.25 to 8:1, preferably about 0.75 to" 4:1, Weights of n-parafi'in per weight of catalyst per hour (WHSV).

Free molecular hydrogen must be present in our reaction system and the hydrogen to n-paraflin molar ratio will usually be from about 0.01 to 20:1 or more, preferably about 2 to 10:1. Conveniently, the hydrogen concentration is maintained by recycling hydrogen-rich gases from the reaction zone. These gases will usually contain hydrogen halide at least after the initial processing period and as there is usually only a small loss'of the halide at processing conditions, the desired concentration in the feed may be maintained merely by recycling the hydrogenhydrogen halide-containing gases with a small make-up of hydrogen halide- ,As previously stated the preferred catalyst base material is an activated or gamma-alumina made by calcining a precursor predominating in alumina trihydrate. An alumina of this type is disclosed in US. Patent No. 2,838,444. The alumina base is'derived from a precursor alumina hydrate composition containing about 65 to 95 weight percent of one or more of the alumina trihydrate forms, gibbsite, bayerite I and bayerite II (randomite) as defined by X-ray difiraction analysis. The substantial balance of the hydrate is amorphous hydrous or monohydrate alumina. Trihydrates are present as Well defined crystallites, that is they are crystalline in form when examined by X-ray diffraction means. The crystallite size of the precursor alumina trihydrate is relatively atomic weight between 35 and 85 as such, an organobromine; monoand polyhalo-alkanes such as carbon tetrachloride, chloroform and tertiary butyl chloride; or other available materials which will be converted under the conditions of isomerization to obtain the desired abouti75 weightpercent on the basis of the catalyst, pref- .erably at least about 80 to 90%. The catalyst base is an activated or gamma-alumina such as those derived by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate or their mixtures. The .catalyst base precursor most advantageously is a mixture predominating, for instance about 65 to 95 weight percent, in one or more of the alumina trihydrates bayerite I, bayerite II (randomite) or gibbsite, and about 5 to 35 weight percent of alumina monohydrate (boehmite), The

oxides such as silica, magnesia, natural or activated clays (such as kaolinite, montmorillonite, halloysite, etc.), Although. the components of the catalyst can vary as stated, a preferred catalyst contains platinum and boria deposited on activated alumina. w

The 'isomerization reaction conditions used in the meth- .,od of the present invention include a temperature sufficient to maintain the n-paraflin feed in the vapor phase for instance ranging from about 2.00 to 1000 p.s.i.g.,

large and usually is in the to 1000 Angstrom unit range. The calcined alumina has a large portion of its pore volume in the pore size range of about 100 to 1000 Angstrom units generally having about 0.1 to about 0.5 and preferably about 0.15 to about 0.3 cc./g. of pore volume in this range. As described in the patent the calcined catalyst base can be characterized by large surface area ranging from about 350 to about 550 or more square meters/gram when in the virgin state as determined, for example, by the BET adsorption technique. A low area catalyst base prepared by treating the predominantly trihydrate base precursor is described in US. Patent No. 2,838,445. This base when in the virgin statehas substantially no pores of radius less than about 10 Angstrom units and the surface area of the catalyst base is less than about 350 square meters/ gram and most advantageously is in the range of about to 300 square meters gram.

The platinum group metal component of the catalyst can be added to the alumina base by known procedures.

For instance, the platinum metal component can be deposited on a calcined or activated alumina, but it is preferred to add the platinum metal component to the alumina hydrate precursor. 'Ihus platinum can be added through reaction of a halogen platinum acid, for incomponent can be provided by mixing an aqueous platinum sulfide sol with the alumina hydrate.

This sol can be made by reaction in an aqueous medium of a halogen platinic acid with hydrogen sulfide. The

.alumina hydrate containing the platinum metal can be 1 dried and calcined usually at a temperature from about .750 to 1200 F. or more to' provide the activated or gamma-alumina modifications. The boria can be added .to the catalyst in any stage of its preparation. It may be incorporated in the support, for instance, by precipitation,,coprecipitation, impregnation, and mulling either 7 before or aftertheadditionof the group VIII'r'ne'tal.

It can also be applied by impregnation from solution 23. (water, organic or inorganic solvents) or from a gas phase. after-it-has been formed bytabletting or extrusion and calcined. After the boria is added in this procedure-thecatalystcan be rccalcined.

The catalyst of the present invention can be easily regenerated employing conventional procedures, for in-- stance by subjecting it to an oxygen-containing gas at temperatures suflicient to burn off. carbon deposited on the catalyst during the conversion of petroleum hydrocarbon feedstock. This oxygen-containing gas, e.g. an oxygen-nitrogen mixture, can contain about 0.01 weight percent to weight percent oxygen but preferably contains about 0.5-to 1.5 weight percent oxygen andiis introduced at a flow rate such that the maximum temperature at the site of combustion is below about 1000 F.

When following the process of the present invention, outstanding selectivity, as an-example, ashigh as 99+%, and good conversions of n-parafiinic hydrocarbon materials to corresponding isomericstructures are provided. For instance, the conversion of n-pentfane to isopentane .is generally about 50 to 70'percent and usually above about 60% based on the pentane feed; about 60 to 85 percent, usually above about 75 percent, of n-hexane .is converted to iso-hexane including about 6 to 20 percent of 2,2-dimethylbutane, a high octane component; and about 35 to 50 percent, usually above about 42 percent, of n-butaue is converted to isobutane.

The parafiinic feed material employed in our process is generally a C to C n-paraflinic-containing cut derived :from crude petroleum hydrocarbons, asby distillation, :reforming and extraction processes. The feed we prefer touse, however, is a blend of n-pentaneand n-hexane :usually containing about 25 percent or moreof'n-hexane and preferably a predominant amount of: n-hexane.

The following specific examples will serve to illustrate our invention but they are not to be considered limiting.

EXAMPLE I (A). Preparation of noble metal aluminacomposition .A noblemetal alumina composition of the kind described in US. Patent No. 2,838,444 can be employed'in preparing the catalyst used in the processof our invention. The composition of this patent can be made as :follows. Pure aluminummetal is dissolvedinpure'hydro- 'chloric acid, and the resulting solution ismixed with deionized water to form an aqueous aluminum chloride solution and an alumina gel is prepared equivalent to approximately 65 grams of A1 0 per liter. A separate deionized water solution of NHr-OH is prepared containing approximately 65 grams of ammonia perliter. These two reagents in approximate volume ratio .of. 141 are intimately mixed as a flowing stream at a pH'ofwSzO. The flowing stream is passed to a stoneware container and an alumina hydrate is visible. The-precipitated hydrate is filtered from the mother liquid and washed to 0.2% chloride-by successive filtrations and reslurryings indeionized water until the desired chloride concentration is reached. In each reslurrying ammonia is added to give a pH of about 9. The washedhydrate is covered, with water; ina container and aged at about 90 F. until it is approximately 70% trihydrate, the remaining being sub? stantially of the amorphous or monohydrate forms. The total hydrate composition is comprised of 42% bayerite, 18% randomite, 11% gibbsite, 20% bo'ehmite and 9% amorphous as determined by X-ray' difirjaction' analysis. The aged hydrate is mixed with deionized Water in a rubb'erlined container to provide a slurry,- of about 7 weight percent A1 0 ata pH of about 8.0. A- chloroplatinic acid solution in deionized water (0.102 gram platinum- Per milliliter) is stirred into the slurry and the slurry is then contacted with a deionized water solution which h'as-been Saturated with at 78* F. to precipitate the platinum.

However,- it is frequently added to the catalyst:

6- The pH of the slurry is adjusted to 6.0 to 6.5 by anmonium. hydroxide addition nd. the, ds; f: 1531 are dried ona horizontaldrumldrisl' 0. g yean wdsr; of generally lessthanZOmesh. Thedmm dried P wde is 1 mixed t in a. planetary. typerdough; beater withsnlficient; deionized'water toindicate 2.6;.weig11t percent:wat r; una,

'Central Scientific Company infra-red moisture meter con;

taining a watt bulb, cat. No. 26675. The resulting mixture is forced through a die plate having holes in diameter bolted to a 3 /2" Welding Engineers screw ex: truder. The resulting strands are broken to particles of length vary-ing generally betweenabout. 5 to.-1.".

The particles are dried at 230 F. and calcined byheat ing to 925 F. ina flow of nitrogen gas followedby a flow of air while the-composition is maintained 'at' a temperature in the range of- 865- to- 920 F. The comp sition thus produced. analyzes about. 0.6. .weightpercent. t inum which is in sufiiciently divided form soto exhibit by X-ray. diffraction studies. the substantial absence; of crystallites or crystals of size larger than 50; Angstrom units. After the calcination the composition-has ari area: (BET method) within the range from about 350191550 square meters/ gram.

(B). Br pa tiorz nob e metal-,bnriae lumina q lalysl.

A P mumina mp sit on prepared ssent a y as described above, except that air was-.u'sed:for the complete ealcination procedure, and containing about 0.6% platinum was employed in. preparing the. noble metalboria-alumina catalyst by the followingprocedure. 300 grams of the calcined platinum aluminacomposition were weighed into a 6" crystallizingdish. 59grams of'H BQ were dissolved in 279 ml. of deionized Water by heatingto boiling. The hot boric acid solution was poured over the catalyst andstirred'thoroughly with a rubber spatula; The catalyst was, placed in a forced air drying oven, set at. 284 F; for 4 'hours.-. The catalyst was stirred occasionally' while drying; The oven dried catalyst was transferred. toa sagg er and placed in a mufile furnace preheated to'1000 F. The catalyst was held .at 1000 F. for 2 hours and cooled in a desiccator. Analysis: 9.95% B 0 (.0) Activation ofnoblemetal-boritt glttminacatalyst;

Although the noble metal-boria-alumina catalyst can be activated during isomerization processing on stream, it can-be pre-reduced or pre-activated. Pro-activation can} be accomplished by treatment with hydrogen at an 616,- vated temperature, for instance" about 80010 1000" F5 Rather than pro-activate the catalyst it can be useddi rect-ly in the isomerization process and the presence ofi the free hydrogen gas Will cause activation in the initial stages of the process;

An example of pre-activation follows: 40, grams of this catalyst were supported on glass beads inthe cent'erof a 1-inch LD. Universal stainless steel reactor. The reactor was set in place in a bronze-block furnace con: trolled by Microswitch thermostats. The catalyst was heated to 800 F. under atmospheric pressure of pure hydrogen' flowing at about 2 cu. ft./h'r, These conditions were maintained for 16 hours, At this time the reactor is cooled to operating temperatures and reaction'conditions are established for-processing the paraflijri feed.

EXAMPLE H The isomerization process of the present invention is illustrated by runs A, B, .C and -D (presented below Table I) employing platinum, palladium, rhodium and platinum, respectively, as the group VIII metal. In adclition, run E employing the'boria-alum-ina. catalyst: Without the group VIII metal is provided for comparison purposes. All runs were conducted under the conditions specifiedabove and the catalysts wereprepared; essentials ly according to the procedure as described in ExampleaI except in the preparation of the catalyst used in rum E,

where the group VHImetal was omitted. The results of these are also presented in this table. 'The yields in weight percent of the isomeric structures in this table and throughout the specification are based on the correspond ing total pentane and hexane structures present in the feed.

cyclopentane plus cyclohexane is fed to a reactor unit containing platinum-'boria-alumina catalyst, prepared-essentially as described in Example I(B) above, with a Ruska pump while the H --HCl was 'fed in by means of a' H HClblend mole percent HCl). The conditions-were' 625 9 F; 300 p.s.i.g., 5/1 'H /HC, 1 WHSV,

TABLE I Rrm 971- 971-11 971-28 971-13 971-2913 A B C D, E

Catalyst:

' Number 480-279-- 480-326 480-210 4 4315 Description Pt-boria on alu- Pd-boria on alu- Rh-boria 0n alu- 0.6% Pt, 10% B2 10%b0r1a on 8111.

mma. mine. a. OaAlzOs. mina. Fee (2). Conditions:

-Ternperature, F.-- m W m 600 600, WHSV 1.0... 1.0-.. 1.0-- 1.0.. Pressure, n 1 2 am am am am Hg/HO (moleratio) 5.0--- 5.0.- 5.0.- 5.0 H01 (weight percent based on hydro- 12.5 i 5 12 5 carbon feed). Yields (weight percent):

i-O 61.5 60.3.- 62.6-- 62.1.- 3, 1 79.9 79.3-- 79.4-- 2,2-DM' 8.4- 13.9.. 134.. Selectivity, C +weight percent 96.2.. 99.0 98.7.- 99

Feed:

(1) Phillips Commercial Grade 11-05-05 blend: Composition:

3% i-Cs; 30.6% 11-05; 8.1% 2,3-DMB+2-MP;

EFFEUI OF BORIA ON THE ALUMINA STRUCTURE The superior characteristics, in the presence of the hydrogen chloride component in the isomerization process of the present invention, of a platinum-boria-alumina composition prepared essentiallyaccording to the procedure as described in Example I above is shown below in comparison with a platinum-alumina composition without the boria and prepared essentially as described in Example I(A) above.

A 5.46 gram portion of commercial Sinclair-Baker RD-lSO catalyst (a platinum-alumina catalyst prepared essentially according to the procedure described in Example I(A) above) was placed in a Pyrex tube. The catalyst was supported on a sintered glass disk to allow gas to pass up, through it. A, thermocouple well was ledfrom the side of the tube into the catalyst bed. Anhydrous hydrogen chloride gas was passed through the catalyst at a rate of about cc./min. at atmospheric pressure. A furnace was placed around the tube, heat was turned on and the temperature inside the thermowell brought to 600 F. The temperature was maintained at 600i-10 F. for 188 hours. The catalyst was purged of HCl withfiowing H for two hours, cooled and removed from the tube.

A 7.00 g. portion of Sinclair-Baker RD-150 catalyst+ 10% B 0 (480-279), was charged to a similar apparatus and treated in an identical manner as Sinclair-Baker RD-150 catalyst described in the previous paragraph. The surface area of each catalyst was determined before and after this treatment. The measurement was made by the BET method using N adsorption at the temperature of liquid nitrogen. The Sinclair-Baker RD-150 catalyst area fell from 500 to 180 square meters/gram while the Sinclair-Baker RD-150 B O catalyst area fell from 380 to 280 square meters/ gram. The results indicate that B 0 has a beneficial efiect on the alumina structure.

IMPURITY TOLERANCE LIMIT 1 The relatively high tolerance limit of a platinum-boriaalumina catalyst for, the aromatic and naphthene contaminants in n-paraflinic containing hydrocarbon feeds employed in an isomerization process is demonstrated below.

.Z'APhillips commercial 'grade n-C -C blend-(-65) containing 4% aromatics and 16 weight percent methyl- EFFECT OF BORIA ON AREA, CRUSH STRENGTH AND SELECTIVITY A charge of platinum-boria-alumina catalyst, prepared essentially as described in Example I above and containing 0.6% platinum and 10% boria, was tested in a gas reactor unit under a variety of processing conditions- Periodic activity checks were taken throughout the testing perlod. Between intervals of hydrocarbon processing the 7 catalyst was blocked in the reactor under a H HCl atmosphere at reaction temperature and pressure. The catalyst was subjected to 900 hours of HCl contact and 160 hours of noncontinuous hydrocarbon processing under conditions including 600 F., 300 p.s.i.g., 5/1 H /HC, 1 WHSV, 12.5 weight percent HCl and using a Phillips commercial grade blend of C and C A similarevaluation was conducted using Sinclair-Baker RD- catalyst. A summary of the area and crush strength results are presented in Figures 1 and 2, respectively.

A similar platinum-boria-alumina catalyst composition after 430 hours of continuous contact with HCl in a glass flow system gave the following results for hydrocarbon processing.

when one compares this result with that obtained for RD-150 after a similar 430 hour treatment with HCl.

Conditions: 7

600 F., 1 WHSV, 5/1H /HC, 300 p.s.i.g., 12.5 weight percent HCl, Phillips C.G. C -C blend.

I 9 Yields:

-i-C 63.5 Total i-C 76.8 2,2-DMB 10.0 C -lselectivity 65.1

In addition to its loss in isomerization selectivity, RD-150 crushing strength after 430 hours of HCl contact (2.1 lbs.) is decreased to zero after only 17 hours of hydrocarbon processing. These results emphasize the inability of RD-150 alone to function catalytically in the presence of HCl.

PROCESS AGING CHARACTERISTICS A charge of platinum-boria-alumina catalyst, prepared essentially as described in Example I above and containing 0.6% platinum and 10% boria, was tested for aging characteristics in a reactor unit. A Phillips commercial grade n-pentanezn-hexane blend (a 32 volume percent n-pentane:68 volume percent n-hexane blend) including 3.2 percent aromatics and 14 percent C naphthenes was conducted to the reactor under conditions (run 14-192) including 600 to 605 F., 600 p.s.i.g., 5/1 mol ratio of H -f-HCl/HC recycle, 0.6/ 1 mol ratio of H +HCl/HC make-up, and l WHSV. The H +HCl/HC make-up was initially employed at a molar ratio of 06/1 with the H containing 5 mol percent HCl, at 550 hours substantially pure hydrogen was substituted as the make-up at the same ratio, at 690 hours the ratio was switched to 0.3/1 with the H containing 5 mol percent I-ICl, and at 1020 hours the ratio was switched to 06/1. This data shows no apparent loss in activity after 1350 hours of processing.

TABLE II Yields (weight percent):

l-Cs yie It is claimed:

1. In a method of isomerizing a C to C n-parafiiniccontaining hydrocarbon feed, the step comprising contacting said feed in the vapor phase with a catalyst at a temperature of about 500 to 800 F., superatmospheric pressure, and in the presence of free hydrogen and while providing about 1 to 25% of a hydrogen halide based on said feed, said catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and about 3 to 20% of boria supported on an activated alumina.

2. The method of claim 1 in which the catalyst contains about 0.1 to 2% of the platinum group metal.

3. The method of claim 1 in which the temperature is about 575 to 650 F. and the feed contains n-pentane and n-hexane.

4. The method of claim 1 in which the noble metal is selected irom the group consisting of platinum, palladium and rhodium, and is about 0.1 to 1% of the catalyst, the boria is about 8 to 15% of the catalyst and the hydrogen halide is hydrogen chloride.

5. The method of claim 1 in which the activated alumina is derived by calcination of an alumina hydrate precursor consisting essentially of about to of alumina trihydrate and about 5 to 35% of a member selected from this group consisting of amorphous hydrous alumina, alumina monohydrate and their mixture, and the activated alumina has an area of about 350 to 550 square meters per gram before use.

6. The method of claim 3 in which the feed contains substantial amounts of aromatic and naphthenic impurifies.

7. The method of claim 1 in which the temperature is about 575 to 650 F. and the noble metal is platinum and is about 0.1 to 1.0% of the catalyst, the boria is about 8 to 15% of the catalyst, the hydrogen halide is hydrogen chloride, and the activated alumina is derived by calcination of an alumina hydrate precursor consisting essentially of about 65 to 95 of alumina trihydrate and about 5 to 35% of a member selected from the group consisting of amorphous hydrous alumina, alumina monohydrate and their mixture, and has an area of about 350 to 550 square meters per gram before use.

8. The method of claim 7 in which the feed contains n-pentane and n-hexane blend.

9. The method of claim 1 wherein the catalyst is prepared by contacting a calcined platinum metal alumina composition with a heated aqueous solution of boric acid and calcining the resulting platinum metal-boria-alumina composition.

10. The method of claim 4 wherein the catalyst is prepared by contacting a calcined platinum metal alumina composition with a heated aqueous solution of boric acid and calcining the resulting platinum metal-boria-alumina composition.

11. The method of claim 1 in which the noble metal is selected from the group consisting of platinum, palladium and rhodium and is about 0.1 to 2 percent of the catalyst, and the boria is about 8 to 20 percent of the catalyst.

12. The method of claim 11 wherein the catalyst is prepared by contacting a calcined platinum metal-alumina composition with a heated aqueous solution of boric acid and calcining the resulting platinum metal-boria-alumina composition.

13. The method of claim 1 wherein the noble metal is selected from the group consisting of platinum, palladium and rhodium and is about 0.1 to 2 percent of the catalyst, and the boria is about 3 to 15 percent of the catalyst.

14. The method of claim 13 wherein the catalyst is prepared by contacting a calcined platinum metal-alumina composition with a heated aqueous solution of boric acid and calcining the resulting platinum metalboria-alumina composition.

References Cited in the file of this patent UNITED STATES PATENTS 2,751,333 Heinemann June 19, 1956 2,798,105 Heinemann et a1. July 2, 1957 2,831,908 Starnes et al. Apr. 22, 1958 2,834,740 Johnson et al. May 13, 1958 2,838,444 Teter et a1. June 10, 1958 

1. IN A METHOD OF ISOMERIZING A C4 TO C9 N-PARAFFINICCONTAINING HYDROCARBON FEED, THE STEP COMPRISING CONTACTING SAID FEED IN THE VAPOR PHASE WITH A CATALYST AT A TEMPERATURE OF ABOUT 500 TO 800*F., SUPERATMOSPHERIC PRESSURE, AND IN THE PRESENCE OF FREE HYDROGEN AND WHILE PRIVIDING ABOUT 1 TO 2K% OF A HYDROGEN HALIDE BASED ON SAID FEED, SAID CATALYST CONSISTING ESSENTIALLY OF ABOUT 0.01 TO 2% OF A PLATINUM GROUP BOBLE METAL AND ABOUT 3 TO 20% OF BORIA SUPPORTED ON AN ACTIVATED ALUMINA. 